linux-kernel - Re: [PATCH 1/2] mm,vmscan: Kill global shrinker lock.

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Message-Id: <201711201956.IIB86978.OFMVFFOJLtOSHQ@I-love.SAKURA.ne.jp>
Date:   Mon, 20 Nov 2017 19:56:28 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     hch@...radead.org, mhocko@...nel.org
Cc:     minchan@...nel.org, ying.huang@...el.com,
        mgorman@...hsingularity.net, vdavydov.dev@...il.com,
        hannes@...xchg.org, akpm@...ux-foundation.org, shakeelb@...gle.com,
        gthelen@...gle.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, paulmck@...ux.vnet.ibm.com
Subject: Re: [PATCH 1/2] mm,vmscan: Kill global shrinker lock.

Christoph Hellwig wrote:
> On Mon, Nov 20, 2017 at 10:42:37AM +0100, Michal Hocko wrote:
> > The patch has been dropped because allnoconfig failed to compile back
> > then http://lkml.kernel.org/r/CAP=VYLr0rPWi1aeuk4w1On9CYRNmnEWwJgGtaX=wEvGaBURtrg@mail.gmail.com
> > I have problem to find the follow up discussion though. The main
> > argument was that SRC is not generally available and so the core
> > kernel should rely on it.
> 
> Paul,
> 
> isthere any good reason to not use SRCU in the core kernel and
> instead try to reimplement it using atomic counters?

CONFIG_SRCU was added in order to save system size. There are users who run Linux on very
small systems ( https://www.elinux.org/images/5/52/Status-of-embedded-Linux-2017-09-JJ62.pdf ).

Also, atomic counters are not mandatory for shrinker case; e.g.
http://lkml.kernel.org/r/201711161956.EBF57883.QFFMOLOVSOHJFt@I-love.SAKURA.ne.jp .